1. Field of the Invention
The present invention relates to an image data filing system and more particularly, to an image data filing system suitable for correcting an image stored in the file and re-storing the corrected image.
2. Description of the Prior Art
Document image file systems (electronic file systems) utilizing large capacity optical disks have recently become noticeable as the new means for document management. Optical disks are large in capacity and capable of recording image data so that document image information such as design layouts, literatures, contracts and etc. can be stored therein. As an example of systems of this kind, there is known, for example, a system disclosed in a magazine "Nikkei Electronics" Mar. 28, 1983, pp. 105 to 120.
It becomes sometimes necessary to partially correct the image data, e.g., design layouts or the like, already stored in such an image file system and re-store the corrected image data. According to the conventional system, an already stored image is made corrected through the method whereby the stored image is first printed out and applied to correction on the printed paper, and the corrected image is read by an image input device to store it in the image file as new image data in place of the image data before the correction.
The conventional system, however, does not consider image quality deterioration resulting from image printing and inputting operations, thus posing a problem that as an image is frequently applied to correction, the quality of such an image, particularly the image portion where correction was not applied, gradually deteriorates. More specifically, since the pixel densities of a printer and an image input device used in such a system are different to each other in most cases, the size of an image such as design layouts is reduced or magnified every correction operation in order to make the sizes of the original image and the corrected image coincide with each other. In addition, since there are digital/analog conversion errors at the printer and image input device, line information of the corrected image is degraded to thus result in distorted lines and increased noises. If the same image data are applied to correction n times, the original image information will have undergone the image input device n+1 times and the printer n times. Consequently, as n becomes large, the image quality deteriorates more remarkably.